Pluronic Triblock Copolymer Research Articles

Mesoporous organosilica with amidoxime groups for CO2 sorption.

Incorporation of basic species such as amine-containing groups into porous materials is a well-established strategy for achieving high uptake of acidic molecules such as CO2. This work reports a successful use of the aforementioned strategy for the development of ordered mesoporous organosilica (OMO) with amidoxime groups for CO2 sorption. These materials were prepared by two-step process involving: (1) synthesis of OMO with cyanopropyl groups by co-condensation of (3-cyanopropyl)triethoxysilane and tetraethylorthosilicate in the presence of Pluronic P123 triblock copolymer under acidic conditions, and (2) conversion of cyanopropyl groups into amidoxime upon treatment with hydroxylamine hydrochloride under suitable conditions. The resulting series of amidoxime-containing OMO was prepared and used for CO2 sorption at low (25 °C) and elevated (60, 120 °C) temperatures. These sorbents exhibited relatively high adsorption capacity at ambient conditions (25 °C, 1 atm) and remarkable high sorption uptake (∼3 mmol/g) at 60 and 120 °C. This high CO2 uptake at elevated temperatures by amidoxime-containing OMO sorbent makes it a noticeable material for CO2 capture.

Sol–gel process for the synthesis of ultrafine MnO2 nanowires and nanorods

A low-temperature sol–gel process associated with different surfactants in ethanol solvent was applied to prepare ultrafine MnO2 nanowires and nanorods. The surfactants used in the synthesis procedure are crucial for the structure of products. Highly dispersed MnO2 nanowires was formed by assistance of cetyltrimethyl ammonium bromide while hierarchical particles assembled with nanowires were synthesized by usage of pluronic P123 triblock copolymer or Polyvinyl pyrrolidone. The free-standing sheet like structure aggregated with nanorods was obtained by using sodium dodecyl sulfate as a surfactant. All samples were characterized by SEM, TEM, XRD and the results indicated these MnO2 ultrafine nanostructures could be expediently produced by this facile method.

In vitro toxicity and bioimaging studies of gold nanorods formulations coated with biofunctional thiol-PEG molecules and Pluronic block copolymers.

In this work, we investigated the cytotoxicity, colloidal stability and optical property of gold nanorods before and after functionalizing them with thiolated PEG and Pluronic triblock copolymer (PEO–PPO–PEO) molecules. The morphology of functionalized gold nanorods was characterized by UV–visible absorption spectroscopy, transmission electron microscopy, and dynamic light scattering. Solution phase synthesis of gold nanorods has remained the method of choice for obtaining varying shapes and aspect ratios of rod nanoparticles. This method typically involves the use of cetyltrimethylammonium bromide (CTAB) surfactants as directing agents to grow gold nanorods in the solution phase. The as-synthesized gold nanorods surfaces are terminated with CTAB molecules and this formulation gives rise to adverse toxicity in vitro and in vivo. To employ the gold nanorods for biological studies, it is important to eliminate or minimize the exposure of CTAB molecules from the gold nanorods surface to the local environment such as cells or tissues. Complete removal of CTAB molecules from the gold nanorods surface is unfeasible as this will render the gold nanorods structurally unstable, causing the aggregation of particles. Here, we investigate the individual use of thiolated PEG and PEO–PPO–PEO as capping agents to reduce the cytotoxicity of gold nanorods formulation, while maintaining the optical, colloidal, and structural properties of gold nanorods. We found that encapsulating gold nanorods with the thiolated PEG or PEO–PPO–PEO molecules guarantees the stability and biocompatibility of the nanoformulation. However, excessive use of these molecules during the passivation process leads to a reduction in the overall cell viability. We also demonstrate the use of the functionalized gold nanorods as scattering probes for dark-field imaging of cancer cells thereby demonstrating their biocompatibility. Our results offer a unique solution for the future development of safe scattering color probes for clinical applications such as the long term imaging of cells and tissues.

Interaction of an Amphiphilic Drug Trifluoperazine Dihydrochloride with Pluronic Triblock Copolymers: A Physicochemical Study

In the present study, we report the interactional behavior of the phenothiazine drug trifluoperazine dihydrochloride (TFP) with Pluronics (L64, F68, and P123) using surface tension, cloud point and fluorescence measurements. Various micellar and interfacial parameters such as critical micellization concentration (cmc), interaction parameter (β), effectiveness of surface tension reduction (πcmc), maximum surface excess concentration (Γmax), and minimum area per molecule (Amin) at the air–water interface have been evaluated using surface tension technique. The phase separation behavior of the drug is studied in the presence of Pluronics, and the corresponding thermodynamic parameters such as Gibbs free energy (ΔG°c), standard enthalpy (ΔH°c), and entropy (TΔS°c) of clouding have been calculated. Employing the steady state fluorescence measurements, the interactions between the drug and Pluronics have been determined in terms of the number of binding sites for drug molecules (n), binding constants (Ka), and Stern–Volmer quenching constants (Ksv).

Niobium incorporated mesoporous silicate, Nb-KIT-6: Synthesis and characterization

The direct incorporation of niobium into ordered cubic large pore mesoporous silicate with Ia3d structure, KIT-6, is demonstrated via hydrothermal synthesis using a Pluronic P123 triblock copolymer as the structure directing agent and n-butanol as additive. The synthesized materials, denoted as Nb-KIT-6, were characterized by analytical techniques such as XRD, elemental analysis, N2 sorption, HR-TEM, 29Si cross polarization (CP) magic angle spinning (MAS) NMR, Diffuse reflectance UV–Vis, NH3-TPD, pyridine-FTIR and H2-TPR. The Nb-KIT-6 materials, prepared with various Nb contents, possess high specific surface area (997–804m2/g) and pore volume (1.46–1.12cm3/g) with uniform pore diameter centered around 9.3nm. The incorporation of most of the Nb in the framework was confirmed by Diffuse reflectance UV–Vis spectra, and contributes to an increase in total acidity. Pyridine FTIR measurements confirm the presence of both Brønsted and Lewis acidic sites, with the total acidity increasing nearly linearly with Nb content.

Complex electrochemical investigation of ordered mesoporous carbon synthesized by soft-templating method: charge storage and electrocatalytical or Pt-electrocatalyst supporting behavior

Ordered mesoporous carbon (OMC) was synthesized by an evaporation induced self-assembly method, under acidic conditions, with resorcinol as the carbon precursor and Pluronic F127 triblock copolymer (EO106PO70EO106) as a structure directing agent. The obtained OMC product was characterized by N2 sorptometry, X-ray diffractometry and Raman spectroscopy. The mean pore radius of 2nm and specific surface area of 712 m2g−1 were found. The OMC sample was subjected to a complex electrochemical testing in order to check for its applicability in various energy conversion processes. For pure OMC, the charge storage properties and kinetics of oxygen reduction reaction (ORR) in alkaline solution were measured. The OMC sample delivered specific capacitance of 232 F g−1 at 5mV s−1 with 83.6% capacitance retained at 100mV s−1. Effective ORR electrocatalysis by OMC in alkaline media was evidenced, with onset potential amounting to −0.10V vs. saturated calomel electrode. A part of the OMC sample was used as a support of Pt nanoparticles, and examined as electrocatalyst for hydrogen evolution reaction (HOR) and ORR in acidic media. Reversible HOR kinetics was observed, while ORR performances were found to be competitive to the ones on other carbon-supported Pt electrocatalysts reported so far. A superb electrochemical behavior was correlated to physico-chemical properties of OMC. Described OMC stands out as a highly versatile material, which can be used to replace carbon materials developed for specific purposes, allowing rationalization of carbon-based technologies aimed for energy conversion purposes.

Sol-gel synthesis, characterisation, and photocatalytic activity of porous spinel Co3O4 nanosheets

AbstractMesoporous spinel Co3O4 nanosheets were synthesised via a simple sol-gel route using the Pluronic P123 triblock copolymer as the stabilising agent. Their structural, morphological, and textural properties were characterised. FTIR spectrum revealed the formation of cobalt oxide without any surface adsorbed impurities. Face centered cubic phase of spinel Co3O4 with the mean crystalline size of 26 nm was assigned by the X-ray diffraction analysis without the formation of other phases. Porous nanosheets and cave-like morphologies were identified from the scanning electron microscopy (SEM) images. Highly agglomerated more or less spherical particles with well separated lattice fringes, representing the oriented growth of nanocrystals, were noticed on the transmission electron microscopy photographs. Surface area analysis revealed that the spinel has high surface area of about 25 m2 g−1 with monomodal mesoporosity. The average pore size distribution was found to be about 15.8 nm. The as-prepared spinel photocatalyst showed a mild photocatalytic activity in the degradation of methylene blue (2.5 mg L−1) under UV light irradiation with air as the oxidising agent. Photocatalytic activity of the as-prepared reusable Co3O4 was found to be higher than that of the commercial spinel powder.

Porous NiOx nanostructures templated by polystyrene-block-poly(2-vinylpyridine) diblock copolymer micelles

A facile synthetic route to NiOx nanostructures using various amphiphilic polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP) diblock copolymers as templates was investigated. The synthesis targets NiOx nanostructures with a large surface area in order to allow an efficient functionalization, e.g., through loading with dyes to enable photo-induced hole injection for use in dye-sensitized solar cells or in (photo-)catalytic systems. The complete synthetic process to NiOx contains several steps: (i) the dissolution of the diblock copolymer, (ii) the subsequent addition of Ni2+, followed by the formation of core–corona micelles and eventually, (iii) further addition of Ni2+, resulting in the formation of a macroscopic precipitate. In all cases, (iv) deposition onto different substrates and calcination yielded NiOx films. All intermediates were thoroughly investigated using scanning or transmission electron microscopy, dynamic light scattering, and UV-vis spectroscopy. In contrast to the well-established synthetic route via the commercially available Pluronic F108 triblock copolymer, in our case a variety of different morphologies was found, i.e. spherical particles, toroid structures, or networks. Furthermore, the obtained BET area of about 50 m2 g−1 is comparable to the value for conventionally obtained NiOx surfaces. First dye sensitization experiments with coumarine 343 confirm that the dye binds to the surface, which is a prerequisite for using the material as a photo-electrode. The presented route to porous NiOx is easy and provides superior control over the morphology of the intermediates involved in nanostructure formation.

SANS study on self-assembled structures of Pluronic F127 triblock copolymer induced by additives and temperature

In the temperature range of 303–333 K, the self-assembled structures of a mixture of Pluronic F127 triblock copolymer [PEO106PPO70PEO106; PEO is poly(ethylene oxide) and PPO is poly(propylene oxide)] and an organic derivative, 5-methyl salicylic acid (5mS), in aqueous solution have been investigated using small-angle neutron scattering (SANS). Above a 5mS concentration of 1.93 g l−1, the F127–5mS mixture solution became cloudy with a blue colour arising from the Tyndall effect, indicating that large polymer aggregates had formed in the mixture solution. SANS measurements showed that the self-assembled structure of the F127–5mS mixture transformed from a spherical to a cylindrical micelle with increasing the concentration of 5mS in the temperature range of 303–323 K. When the 5mS concentration was increased to 3.3 g l−1, the self-assembled structure of the F127–5mS mixture at 333 K underwent an additional phase transition from a cylindrical to a spherical micelle of large size at a 5mS concentration of 2.75 g l−1, although its self-assembled structure changed from a spherical to a cylindrical micelle at a 5mS concentration of 1.93 g l−1as well. The phase transitions are explained by the variation of the mass fraction of the hydrophilic part of F127 and the coupled effect of the limited solubility and the strong tendency to bind with amphiphilic molecules of 5mS. Using a simple material balance equation and the structural information obtained from SANS model analyses, the numbers of D2O and of 5mS molecules in the core and corona regions are calculated. This result can provide a simple and easy way to prepare various nanostructures using a Pluronic triblock copolymer in aqueous solution and may be very useful for practical applications of a Pluronic polymer such as various nanobuilding blocks or nanotemplates.

Synthesis of 2-hydroxypropyl-β-cyclodextrin/pluronic-based polyrotaxanes via heterogeneous reaction as potential Niemann-Pick type C therapeutics.

Five polyrotaxanes were synthesized by threading 2-hydroxypropyl-β-cyclodextrin (HP-β-CD) onto a variety of α,ω-ditriethylenediamino-N-carbamoyl-poly-(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (Pluronic) triblock copolymers using a two-pot strategy under heterogeneous, nonaqueous conditions. The threaded HP-β-CD units were retained on the pseudopolyrotaxane precursors by end-capping the branched diamine termini with sodium 2,4,6-trinitrobenzene sulfonate. Inclusion of the Pluronic copolymers within the HP-β-CD cavities was more favorable in nonpolar solvents, such as diethyl ether and n-hexane, both of which gave better coverage ratios than polar solvents. (1)H NMR and MALDI-TOF were used to estimate the average molecular weights of the purified polyrotaxane products. A globular morphology of aggregated polyrotaxanes was observed by tapping-mode AFM imaging of dried samples. Treatment of Niemann-Pick C (NPC) type 2-deficient fibroblasts with the polyrotaxane derivatives produced substantial reductions in sterol accumulation, as seen by diminished filipin staining in these cells, suggesting that Pluronic-based polyrotaxanes may be promising vehicles for delivery of HP-β-CD to cells with abnormal cholesterol accumulation.

A study of bottom-up electroplated copper filling by the potential difference between two rotating speeds of a working electrode

In order to achieve a bottom-up plated copper filling with a minimal surface thickness, an additive system containing a pluronic triblock copolymers, ethylene oxide terminal blocks termed EPE as a suppressor, bis(3-sulfopropyl) disulfide (SPS) as accelerator, Janus Green B (JGB) as leveler, and Cl− was used to investigated bottom-up filling by galvanostatic measurements method and cross-sectional OM observation. The EPE-8000 not only was a stronger inhibition for electrodeposition copper reaction, but also had a stronger forced convection with JGB and Cl− in copper electroplating solution than PEG-8000 for copper deposition. The potential difference obtained from two different rotating speeds of a copper working electrode by galvanostatic measurements reached positive 20mV with an addition of the EPE-8000 and was much higher than that with an addition of PEG-8000 (about 12mV), which led to a high filling performance with a minimal surface copper thickness. The effects of additives SPS, JGB, and Cl− on the potential difference and bottom-up filling behavior were investigated in detail. With an addition of EPE-8000, the filling performance of the plating copper solution was enhanced, the surface thickness of deposited copper film was reduced, but also the operation windows of four additives were widened extensively.

Hydrothermal synthesis of mesostructured ZnO micropyramids with enhanced photocatalytic performance

The present article reports the synthesis, characterization and photocatalytic performance of highly oriented three dimensional ZnO micropyramids obtained by the surfactant assisted precipitation- hydrothermal treatment. Pluronic P-123 triblock copolymer was the surfactant employed in the present synthesis. The synthesized ZnO material was characterized for its phase and morphological studies. X-ray diffraction patterns suggested the formation of pure hexagonal wurtzite phase with the mean crystalline size of 39nm. Electron microscopic studies of the material revealed the hexagonal micropyramid like morphology with an approximate size of 1–3μm and the ZnO was found to be single crystalline by the SAED analysis. The ZnO micropyramids provided a bimodal mesoporous texture with a low specific surface area (4.5m2/g). Optical properties investigated using the photoluminescence spectrum indicated that the ZnO has a broad UV and blue emission bands which were attributed due to the annihilation of excitons, and a broad visible green emission corresponds to the oxygen interstitial defects. Under the UV light illumination, several concentrations of methylene blue were degraded completely over the as-synthesized ZnO microcrystals for repeated cycles.

Combination of dry reforming and partial oxidation of methane over Ni catalysts supported on nanocrystalline MgAl2O4

In this paper CO2 reforming combined with partial oxidation of methane was carried out over MgAl2O4 supported Ni catalysts with various Ni loadings. MgAl2O4 with high specific surface area was synthesized by co-precipitation method with the addition of pluronic P123 triblock copolymer as surfactant. The results demonstrated that methane conversion in combined reforming is significantly increased with increasing the Ni content. The 7wt.% Ni/MgAl2O4 catalyst showed no carbon formation in combined and partial oxidation of methane. The long term stability test was also showed high catalytic stability for 7% Ni/MgAl2O4 catalyst in combined, partial oxidation and dry reforming of methane.

Synthesis and characterization of large pore cubic mesoporous silicas functionalized with high contents of carboxylic acid groups and their use as adsorbents

Well-ordered cubic FDU-12 type mesoporous silicas functionalized with various contents of carboxylic acid group (COOH), up to 40mol% based on silica, were synthesized via co-condensation of tetraethyl orthosilicate (TEOS) and carboxyethylsilanetriol sodium salt (CES) under acidic conditions using Pluronic F127 triblock copolymer as template. The materials thus obtained were characterized by a variety of techniques including powder X-ray diffraction (XRD), nitrogen adsorption–desorption, transmission electron microscopy (TEM), 13C and 29Si solid-state nuclear magnetic resonance (NMR) measurements. The materials were used as adsorbents for removal of methylene blue (MB) in aqueous solutions and as an antidote for intoxication of herbicide paraquat (PQ). Due to the COOH functionalization, three-dimensional pores, high surface areas, and electrostatic interactions between the adsorbent and the adsorbates, the prepared adsorbents possessed very high adsorption capacities and extremely rapid rates for MB and PQ adsorption. The kinetic regression results revealed that the overall adsorption process was controlled by external mass transfer and intra-particle diffusion jointly. The Langmuir isotherm model showed better fit with the experimental adsorption data than the Freundlich isotherm model, implying a monolayer adsorption mechanism. The present results show that the prepared COOH functionalized cubic mesoporous silicas have great potentials for removing pollutants and herbicides from aqueous solutions in environmental and clinical applications.

Tungsten-incorporated cage-type mesoporous silicate: W-KIT-5

Tungsten-incorporated cage-like cubic three-dimensional mesoporous silicate, KIT-5, was successfully synthesized by one-step direct hydrothermal synthesis procedure employing Pluronic F127 triblock copolymer as the structure directing agent under acidic conditions. The resulting material, labeled as W-KIT-5, was characterized by XRD (SAXS and WAXS), N2 sorption, HR-TEM, DR-UV–Vis, 29Si MAS NMR, Raman spectroscopy, H2-TPR and NH3-TPD to better understand the morphology, textural properties and nature of tungsten coordination. With an increase in tungsten content, the surface area decreased from 964 (for Si/W=100) to 425m2/g (Si/W=10) and the corresponding total pore volumes decreased from 0.68 to 0.42cm3/g. Interestingly, narrow pore size distributions centered around approximately 9.1nm were observed for all W-KIT-5 samples. Depending on the loading, the incorporated tungsten is shown to exist in the KIT-5 framework as well as in the extraframework position by complementary analytical techniques. The W-KIT-5 samples are also shown to possess low to medium type acid strength.

Synthesis and characterization of mesoporous Ni–Co oxy-hydroxides for pseudocapacitor application

Mesoporous binary nickel–cobalt (Ni–Co) oxy-hydroxides have been obtained through the microwave-assisted hydrothermal annealing (MAHA) method. The porosity control of the nanostructured Ni–Co oxy-hydroxide nanoparticles is achieved through adding the pluronic triblock copolymer F127 as the surfactant. The structural and electrochemical properties of porous Ni–Co oxy-hydroxide nanostructures are characterized by means of X-ray diffraction (XRD), Brumauer–Emmett–Teller (BET) analysis, transmission electron microscopy (TEM), thermogravimetric analysis (TGA) and cyclic voltammetry (CV). The electrochemical measurement demonstrates that the Ni–Co oxy-hydroxides calcined at 200°C are able to deliver a specific capacitance of 636Fg−1 in 1M NaOH, suggesting their high potential as a novel electrode material of pseudocapacitors with good electrochemical reversibility. In the asymmetric supercapacitor test, the positive electrode is Ni–Co oxy-hydroxide and negative electrode is activated carbon. The specific energy and power, measured at 2Ag−1, for this asymmetric combination are equal to ca. 17Whkg−1 and 1.6kWkg−1, respectively.

Solubilization and Release of a Model Drug Nimesulide from PEO–PPO–PEO Block Copolymer Core–Shell Micelles: Effect of Size of PEO Blocks

The commercially available polypropylene oxide (PPO)–polyethylene oxide (PEO) symmetrical triblock copolymers (Pluronics®) have been recognized as pharmaceutical excipients and used in a variety of applications. This paper reports studies on micellar and solubilization behavior of three PEO–PPO–PEO block copolymers, viz. P103, P104 and P105 (same PPO mol. wt = 3250 g·mol−1 but different % PEO = 30, 40 and 50 %, respectively) in aqueous solutions. Critical micellization concentrations (CMCs), critical micellization temperatures (CMTs), and micelle size/polydispersity for copolymers with and without the drug, nimesulide (NIM), are reported. The solubilization of NIM is significantly enhanced with increasing hydrophobicity (P103 > P104 > P105), concentration, temperature and in the presence of added salt. The copolymer hydrophobicity, temperature and the drug loading strongly affect micelle behavior. The micelle–water partition coefficient (P) and thermodynamic parameters of solubilization, viz. Gibbs energy (\( \Updelta G_{s}^{\text{o}} \)), enthalpy (\( \Updelta H_{s}^{\text{o}} \)) and entropy (\( T\Updelta S_{s}^{\text{o}} \)), were calculated. The solubilization site of the drug in different micellar solutions and its release from Pluronics® micelles in phosphate buffer saline (PBS) solution at 37 °C were examined. The kinetics of NIM exhibits burst release characteristics, which are believed to be controlled by degradation of the copolymers. These studies were carried out to investigate the feasibility of using Pluronics® as a release vehicle of nimesulide in vitro. From the results, it was concluded that Pluronic® based formulations might be practical for drug delivery.

Impact of Synthesis Methods on the Transport of Single Walled Carbon Nanotubes in the Aquatic Environment

In this study, a systematic approach has been followed to investigate the fate and transport of single walled carbon nanotubes (SWCNTs) from synthesis to environmentally relevant conditions. Three widely used SWCNT synthesis methods have been investigated in this study including high pressure carbon monoxide (HiPco), SWeNT CoMoCat, and electric arc discharge technique (EA). This study relates the transport of three SWCNTs (HiPco-D, SG65-D, and P2-D) with different synthesis methods and residual catalyst content revealing their influence on the subsequent fate of the nanotubes. To minimize nanotube bundling and aggregation, the SWCNTs were dispersed using the biocompatible triblock copolymer Pluronic, which allowed the comparison in the transport trends among these SWCNTs. After purification, the residual metal catalyst between the SWCNTs follows the trend: HiPco-D > SG65-D > P2-D. The electrophoretic mobility (EPM) and hydrodynamic diameter of SWCNTs remained insensitive to SWCNT type, pH, and presence of natural organic matter (NOM); but were affected by ionic strength (IS) and ion valence (K(+), Ca(2+)). In monovalent ions, the hydrodynamic diameter of SWCNTs was not influenced by IS, whereas larger aggregation was observed for HiPco-D with IS than P2-D and SG65-D in the presence of Ca(2+). Transport of HiPco-D in the porous media was significantly higher than SG65-D followed by P2-D. Release of HiPco-D from porous media was higher than SG65-D followed by P2-D, though negligible amount of all types of SWCNTs (<5%) was released. Both transport and release patterns follow a similar trend to what was observed for residual metal catalysts in SWCNTs. Addition of NOM increased the transport of all SWCNTs primarily due to electrosteric repulsion. HiPco-D was notably more acidic than SG65-D followed by P2-D, which is similar to the transport trend. Overall, it was observed that the synthesis methods resulted in distinctive breakthrough trends, which were correlated to metal content. These findings will facilitate the safe design of environmental friendly SWCNTs by minimizing mobility in aquatic environments.

Synthesis and characterization of Zirconium incorporated ultra large pore mesoporous silicate, Zr–KIT-6

Zirconium was incorporated into ultra large pore mesoporous silicate, KIT-6, for the first time via hydrothermal synthesis using a Pluronic P123 triblock copolymer as the structure directing agent and n-butanol as additive. Various characterization tools such as XRD, elemental analysis, N2 sorption, HR-TEM, 29Si MAS NMR, DR-UV–Vis and NH3-TPD were employed to understand the morphology, textural properties, structure and the nature of Zirconium coordination. The Zr–KIT-6 samples possess a very high specific surface area of ∼740m2/g with pore volume of ∼1.1cm3/g. An average pore size of about 9nm is evident from N2 sorption and HR-TEM studies. Even though the majority of Zr is incorporated in the silicate framework, highly dispersed ZrO2 nanoparticles are evident in all the samples. The Zr–KIT-6 is also shown to possess acid sites of medium strength.

Kinetics of the Sphere-to-Rod like Micelle Transition in a Pluronic Triblock Copolymer

The kinetics of the sphere-to-rod transition was studied in aqueous micelle solutions of triblock copolymer poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) pluronic P103 (PEO(17)PPO(60)PEO(17)). This transition was triggered by a temperature jump from the sphere phase to the rod phase and monitored with dynamic light scattering. The combination of the scattering intensity and the hydrodynamic radius were used to show that the micelles grow steadily as rods throughout the growth process. The transition was found to exhibit a single exponential behavior even in the case of large deviations from equilibrium. The linear increase in the decay rate with increasing copolymer concentration shows that the transition is dominated by a mechanism involving fusion and fragmentation of proper micelles. The decays of the sphere-to-rod transition were simulated for two pathways: random fusion fragmentation and successive addition of spherical micelles to rods. We show that micelle growth most likely occurs via random fusion-fragmentation. The second order rate constant for fusion and the fragmentation rate are calculated for the case of random fusion-fragmentation.